Methods and devices for determining intermodulation distortions

Abstract

A method ( 300 ) for determining inter-modulation distortions products of a mixing stage includes: driving ( 301 ) a signal input of the mixing stage based on an input signal, wherein an amplitude of the input signal is switched between a first level and a second level, and wherein a frequency of switching the amplitude is smaller than a frequency of the input signal; detecting ( 302 ) at a signal output of the mixing stage a first output signal responsive to the driving of the signal input with the input signal, wherein the amplitude of the input signal is switched to the first level, and a second output signal responsive to the driving of the signal input with the input signal, wherein the amplitude of the input signal is switched to the second level; and determining ( 303 ) the inter-modulation distortions based on the first output signal and the second output signal.

The invention claimed is: 
     
       1. A method for tuning a mixing stage, the method comprising:
 driving a signal input of the mixing stage with an input signal, wherein an amplitude of the input signal is switched between a first level and a second level, and wherein a frequency of switching the amplitude is smaller than a frequency of the input signal; 
 detecting at a signal output of the mixing stage a first output signal responsive to the driving of the signal input with the input signal, wherein the amplitude of the input signal is switched to the first level, and a second output signal responsive to the driving of the signal input with the input signal, wherein the amplitude of the input signal is switched to the second level; and 
 tuning at least one operational parameter of the mixing stage in accordance with an optimization criterion with respect to the first output signal and the second output signal. 
 
     
     
       2. The method of  claim 1 , wherein the at least one operational parameter of the mixing stage is maintained between successive first levels and second levels of the amplitude of the input signal and modified when the amplitude of the input signal is switched from the second level to the first level. 
     
     
       3. The method of  claim 1 , wherein the optimization criterion is based on a minimum difference between the first output signal and the second output signal. 
     
     
       4. The method of  claim 1 , further comprising:
 switching the mixing stage to a calibration mode in which the mixing stage is disabled for receiving communication signals when performing the tuning of the mixing stage. 
 
     
     
       5. The method of  claim 1 , further comprising:
 calibrating the mixing stage with operational parameters fulfilling the optimization criterion when enabling the mixing stage for receiving payload signals. 
 
     
     
       6. A calibration device for calibrating a mixing stage comprising a signal input and a signal output, the calibration device comprising:
 a signal driver couplable to the signal input, wherein the signal driver is configured to drive the signal input with an input signal, wherein an amplitude of the input signal is switched between a first level and a second level, and wherein a frequency of switching the amplitude is smaller than a frequency of the input signal; 
 a signal detector couplable to the mixing stage signal output, wherein the signal detector is configured to detect at the signal output a first output signal responsive to the driving of the signal input with the input signal, wherein the amplitude of the input signal is switched to the first level, and a second output signal responsive to the driving of the signal input with the input signal, wherein the amplitude of the input signal is switched to the second level; and 
 a tuner configured to tune at least one operational parameter of the mixing stage in accordance with an optimization criterion with respect to the first output signal and the second output signal. 
 
     
     
       7. The calibration device of  claim 6 , wherein the optimization criterion is based on a minimum difference between the first output signal and the second output signal. 
     
     
       8. The calibration device of  claim 6 , further comprising:
 a switch configured to switch the signal input of the mixing stage to the signal driver when the mixing stage is in a calibration mode and to switch the signal input of the mixing stage to a receive port configured to receive communication signals when the mixing stage is not in the calibration mode. 
 
     
     
       9. The calibration device of  claim 6 , wherein
 the calibration device is integrated with the mixing stage on a chip; or 
 the calibration device is an external unit couplable to the mixing stage. 
 
     
     
       10. The calibration device of  claim 6 , further comprising:
 a synchronization unit configured to synchronize the signal driver between driving the signal input with the input signal, wherein the amplitude of the input signal is switched to the first level, and driving the signal input with the input signal, wherein the amplitude of the input signal is switched to the second level. 
 
     
     
       11. The calibration device of  claim 10 , wherein
 the synchronization unit comprises a synchronization clock, wherein synchronizing of the signal driver is based on the synchronization clock, and 
 wherein a frequency of the synchronization clock is smaller than a frequency of a local oscillator of the mixing stage. 
 
     
     
       12. The calibration device of  claim 11 , wherein the signal driver comprises:
 a variable attenuator configured to attenuate the input signal in accordance with an attenuation level; and 
 a level controller configured to control the attenuation level of the variable attenuator. 
 
     
     
       13. The calibration device of  claim 12 , wherein
 a first attenuation level corresponds to the first level of the amplitude of the input signal; and 
 a second attenuation level corresponds to the second level of the amplitude of the input signal. 
 
     
     
       14. The calibration device of  claim 11 , further comprising:
 an integrator configured to integrate the first output signal and the second output signal. 
 
     
     
       15. The calibration device of  claim 14 , wherein the synchronization unit is configured to synchronize the integration of the first output signal with the integration of the second output signal based on the synchronization clock. 
     
     
       16. A radio receiver, comprising:
 a complex mixing stage comprising a local oscillator, wherein the complex mixing stage is configured to mix an input signal at a mixing stage input to provide an in-phase mixed signal at a first channel output and a quadrature mixed signal at a second channel output; 
 a signal driver coupled to the mixing stage input, wherein the signal driver is configured to drive the mixing stage input with an input signal, wherein an amplitude of the input signal is switched between a first level and a second level, and wherein a frequency of switching the amplitude is smaller than a frequency of the input signal; 
 a first signal detector coupled to the first channel output, wherein the first signal detector is configured to detect at the first channel output a first channel first output signal responsive to the driving of the mixing stage input with the input signal, wherein the amplitude of the input signal is switched to the first level and a first channel second output signal responsive to the driving of the mixing stage input with the input signal, wherein the amplitude of the input signal is switched to the second level; 
 a second signal detector coupled to the second channel output, wherein the second signal detector is configured to detect at the second channel output a second channel first output signal responsive to the driving of the mixing stage input with the input signal, wherein the amplitude of the input signal is switched to the first level and a second channel second output signal responsive to the driving of the mixing stage input with the input signal, wherein the amplitude of the input signal is switched to the second level; and 
 a tuner configured to tune at least one operational parameter of the complex mixing stage in accordance with an optimization criterion with respect to the first channel first output signal, the first channel second output signal, the second channel first output signal, and the second channel second output signal. 
 
     
     
       17. The radio receiver of  claim 16 , wherein the optimization criterion is based on a minimum difference between the first channel first output signal and the first channel second output signal and further based on a minimum difference between the second channel first output signal and the second channel second output signal. 
     
     
       18. The radio receiver of  claim 16 , further comprising:
 a switch configured to switch the mixing stage input between the signal driver and a receive port couplable to a receive antenna. 
 
     
     
       19. The radio receiver of  claim 16 , further comprising:
 a second local oscillator tuned to a transmitter frequency, wherein the input signal is generated based on a frequency of the second local oscillator; and 
 a low frequency clock synchronizing the signal driver switching the amplitude of the input signal between the first level and the second level.